Control of a solar parabolic trough based on exposure time

Temperature control of heat transfer fluids plays an important role in the efficiency of concentrating solar power (CSP) systems that are used to convert solar energy to thermal and electrical energy. In this paper the temperature control of a parabolic trough system is considered. Several factors may affect the temperature of the fluid such as the solar exposure time and the solar power variability. A partial differential equation (PDE) is employed to describe the dynamics of the temperature of the heat transfer fluid, where the speed of the fluid is the manipulated variable. The control problem is formulated by interpreting the solution of the PDE from the material derivative description point of view. With this approach it is possible to mitigate the presence of the large varying time delay of the process. The impact of the temperature on the parameters of the process and on the control law is evaluated. The assessment of the control law is done in two scenarios. In the first scenario, a direct measurement of the solar radiation is assumed, but in the second scenario the solar radiation is considered as unmeasured perturbation. In both cases the control law has a good performance.